Anatomical Differences in the Abdominal Wall Between Species with Implications for the Transversus Abdominis Plane Block

With the increased use of simulation based training using animal models for the education of surgical and anaesthetic techniques, an increased understanding of the anatomy of such models and how they compare to humans is required. The transversus abdominis plane block is a regional anaesthetic technique that requires an understanding of the abdominal wall anatomy along with proficient ultrasound use. The current review aims to compare the anatomy of the abdominal wall across species, particularly focussing on the pertinent differences within the class of mammals, and secondarily, it aims to address the implications of these differences for simulation based training of the transversus abdominis plane block. To achieve this, the PubMed, Web of Science and Google Scholar databases were searched for relevant literature. The mammalian abdominal wall differs in its musculature, vasculature or innervation from that of amphibians, birds or reptiles, however, among species of mammals, the structure of the abdominal wall follows a similar framework. Particular differences among mammals include the additional muscular layer of the panniculus carnosus found in most mammals other than humans, the variable arterial origins and dominant vascular supply of the abdominal wall and the number of thoracolumbar nerves innervating the abdominal wall. When using animal models for simulation based training, the pig is recommended for the transversus abdominis plane block given its closely homologous abdominal wall structure, availability and larger comparative size.